Flotation of lateritic nickel ores

ABSTRACT

A process for the beneficiation of nickel bearing laterite ores by means of froth flotation wherein a dispersed pulp of the ore is conditioned with a fatty acid type collecting agent either at an elevated pH to produce, following flotation, an enriched flotation tailing or at a reduced pH to produce, following flotation, an enriched flotation concentrate.

United States Patent 1 Weston 51 Jan. 16, 1973 [54] FLOTATION OF LATERITIC NICKEL [21] Appl. No.: 869,375

[30] Foreign Application Priority Data Dec. 13, 1968 Canada ..037788 [52] US. Cl. ..241/20, 209/5, 209/166 [51] Int. Cl. ..B02c 15/00, B03d 1/02 [58] Field of Search ..209/166, 167; 241/20, 24

[56] References Cited UNITED STATES PATENTS 2,125,631 8/1938 Gutzeit 209/l66 3,473,656 10/1969 Ser ...209/l66 X 3,589,622 6/1971 Weston ..209/166 FOREIGN PATENTS OR APPLICATIONS 534,235 12/1956 Canada ..209/106 917,912 9/1946 France ..209/166 OTHER PUBLICATIONS Chem. Abstracts, 66, 4990 w, 1967.

Elms, Oct. 1968, pp. 74-77, Nickel Laterites.

The Winning of Nickel, Boldt, pp. 9-14, 1968, Longmans Canada Limited, Toronto.

Primary la'xaminer-Frank W. Luttcr Assistant Examiner-Robert Halpcr Att0rneySmart and Biggar [57] ABSTRACT A process for the beneficiation of nickel bearing laterite ores by means of froth flotation wherein a dispersed pulp of the ore is conditioned with a fatty acid type collecting agent either at an elevated pH to produce, following flotation, an enriched flotation tailing or at a reduced pH to produce, following flotation, an enriched flotation concentrate.

10 Claims, No Drawings FLOTATION OF LATERITIC NICKEL ORES BACKGROUND OF THE INVENTION This invention relates to the beneflciation of nickel bearing laterite ores by means of froth flotation.

As is well known, nickel-bearing laterites occurring in large deposits in various parts of the world constitute the biggest reserve of nickel ores presently known. These laterites vary in their nickel, cobalt and iron contents and all are of a generally similar type with a mineral structure about which very little is known excepting that the ultimate crystal structure is in the sub micron size range. The laterites generally have been regarded as being completely refractory to beneflciation by froth flotation and indeed the only commercial beneficiation which is presently known to be carried on consists in a size separation whereby a particular laterite deposit situated in the western United States is beneficated from approximately 1.4 to 1.6 percent nickel by removal of a coarse size fraction containing about 0.7 to 1 percent nickel. This is justifiable because of the high cost of the subsequent treatment processes currently required to recover the nickel from these laterite ores.

SUMMARY OF THE INVENTION I have discovered that, contrary to current opinion in the art, it is possible to employ froth flotation techniques to obtain a useful degree of beneficiation with respect to the nickel minerals contained in the nickel bearing laterites by observing certain specific procedures which will be explained hereinafter.

By means of the process of the present invention, I have found it possible, through the use of economic quantities of various reagents, to beneficiate the laterites with respect to their nickel content by a ratio of concentration of up to approximately 75 percent over the head analysis of the original ore. These I beneflciated ores which are the product of the process of the present invention can be used as a feed material for the currently used nickel recovery processes which could not economically treat the ore in its non beneficiated state, or as an enriched feed showing economic advantage over treatment of the ores in their natural state where such processes can accept as feed such ores.

According to the invention the laterite ore to be treated is comminuted in a wet comminution circuit to substantially its natural grain size distribution. This will normally result in an essentially all slime product from the milling circuit and for optimum results will require the use of wetting agents and/or dispersing agents to maintain adequate flowability of the pulp during comminution. The pulp from the comminution circuit may, as a result of comminution in the presence of the wetting agents and/or dispersing agents, be sufficiently dispersed so that the individual particles or ore within it can behave as independent particles, but if it is not, it is important that the pulp be subjected to further conditioning with or without the addition of further dispersing and/or wetting agents until such condition exists. In some cases, depending upon the specific nature of the particular ore being treated, relatively large quantities of dispersing agent may be required. In other cases, no additional dispersing agent will need to be added at this point. The pulp is then conditioned in the presence of an appropriate amount of a fatty acid type collecting agent for a period which may vary considerably depending upon the nature and quantity of the wetting and/or dispersing agents which it has been necessary to add in the previous dispersion stage. During this conditioning, adjustments may be made to the pH to determine whether the nickel minerals will tend to concentrate in the froth of a subsequent flotation or in the tailings.

ONE ALTERNATIVE MODE OF OPERATION If during the initial dispersion stage of the process, it has been necessary to use relatively large quantities of dispersing agents, in order to bring the pulp to the desired degree of dispersion, it will be usual for the pH of the resulting pulp to end up at a relatively high value by reason of the fact that generally speaking the preferred dispersing agents are alkaline in character. Suitable dispersing agents are, for instance, sodium silicate, sodium hydroxide, or a combination of sodium silicate and sodium hydroxide. In such case the nickel minerals tend to be depressed and the resulting float, made substantially at the final pH of the conditioning stage, will produce a concentrate which is relatively low in nickel and a tailing which is relatively high in nickel. In this case, the tailing together with such of the cleaner tailings as may be economically combined with it forms the desired product of the invention.

ANOTHER ALTERNATIVE MODE OF OPERATION On the other hand, where it has not been necessary to use relatively large quantities of alkaline dispersing agents in order to bring the initial pulp into the necessary state of dispersion, the pH of the pulp at the end of the conditioning stage will be close to the neutral point and if then the pH of the pulp is adjusted with an acid reagent to lower the pH thereof to slightly below the neutral point and the pulp is further conditioned while the pH thereof slightly rises either through the action of naturally present acid absorbing ingredients in the ore, or through the addition of further alkali acting dispersing agents, the result of a subsequent froth flotation will be that the nickel minerals tend to concentrate in the froth and the tailing will be correspondingly low in nickel. In such a case the flotation concentrate represents the desired product of the process.

In the case where relatively large quantities of alkali acting dispersing agents have been used and the pH of the pulp is correspondingly high following the conditioning stage, it is still possible by adding sufficient acid reagent to lower the pH of the pulp slightly below the neutral point and then subjecting the pulp to further conditioning while the pH rises slightly owing to the natural occurrence of acid absorbing constituents in the ore, or by further addition of alkali acting dispersing agents to produce a nickel enriched froth flotation concentrate and a low nickel froth flotation tailing. Generally speaking, however, the additional reagent necessary to lower the pH and then let it slightly rise, and the additional time involved in this additional treatment will make it more economically desirable in such cases to carry out the froth flotation at the higher pH to produce a nickel enriched froth flotation tailing.

EXAMPLES OF THE OPERATION OF THE INVENTION The invention is illustrated by the following examples of the process of the invention as carried out on a laboratory scale employing a laboratory rod mill and ball millfor the comminution of the ore. and a Fagergren laboratory froth flotation unit. In the following examples, pHs were recorded using a conventional glass electrode type pH meter and the assay of iron in the various products was done by conventional chemical analysis. The assay for nickel in the various products was carried out by chemical analysis or atomic absorption. Manipulative procedures were standardized throughout.

EXAMPLE 1 A 1 ,000 gm sample of nickel bearing laterite ore sup plied by Hanna Mining Company of Cleveland, Ohio, was comminuted in a laboratory rod mill for 20 minutes at a pulp density of 50 percent solids in the presence of 59 pounds per ton of sodium silicate. The resulting pulp was transferred to a laboratory Fagergren flotation unit and approximately pounds per ton of fatty acid collecting agent and approximately 2 pounds per ton of sodium hydroxide were added and the pulp was conditioned for a period of 90 minutes. Approximately 4 pounds per ton of sulphuric acid was added bringing the pH of the pulp to 7.9 and the pulp was further conditioned for a period of 30 minutes at which time the pH of the pulp was 8.3. The addition of approximately 1 pound per ton of sodium hydroxide raised the pH to 8.5 and the pulp was then subjected to froth flotation with the following metallurgical results:

Weight Fe Assay Ni Conc. 32.42 7.16 2.528 3 Cleaner 16.31 8.04 3.089 2 Cleaner 17.23 8.76 3.170 1 Cleaner 17.33 9.33 3.572 Rougher Tails 16.71 9.33 3.735

It is to be noted that the final concentrate assayed 2.528 percent nickel as against a rougher tailing which assayed 3.735 percent nickel.

EXAMPLE II A 1,000 gm sample of the same ore as that used in Example I was comminuted in a laboratory ball mill for minutes at a pulp density of 50 percent solids in the presence of 0.2 lbs. per ton of wetting agent (a trimethyl nonyl ether of polyethylene glycol) together with 30 lbs. per ton of sodium silicate. Following the grinding stage the pulp was transferred to a laboratory flotation cell and conditioned for 5 minutes. Following this conditioning stage 5 lbs. per ton of fatty acid collecting agent and 6 lbs. per ton of fuel oil were added and the pulp conditioned for 14 minutes. The pH of the pulp during this conditioning state was 7.7. At the end of this conditioning stage approximately 2 lbs. per ton of sulphuric acid was added and the pulp conditioned for 15 minutes. The pH at the beginning of this conditioning stage was 6.8 and the pH at the end of this stage was 7.1. 18 lbs. per ton of sodium silicate was then added to the pulp and conditioned for 30 minutes. The pH was 8.35 to 8.4. All these stages were carried out in a 600 gram Fagergren laboratory cell. The pulp was by Weight Nickel Iron Rougher Tailing 47.9 1.25 22.2 Cleaner Tailing 16.1 1.31 21.9 36.0 1.94 26.1

Cleaner Conc.

This test illustrates the normal cleaning cycle in the fatty acid flotation circuit as far as the nickel is concerned.

EXAMPLE III 1,000 gm of the same lateritic ore as used in Example 11 was ground in the laboratory ball mill at 50 percent solids for 12 minutes with 14 lbs. per ton of sodium silicate only added to the grinding circuit. No wetting agent was used. Following the grinding stage the pulp was transferred to a 600 gram cell and conditioned for 10 minutes followed by a second conditioning stage of 15 minutes with the addition of approximately 3 lbs. per ton of fuel oil and 7 lbs. per ton of fatty acid. The pH in this stage was 7.05 to 7.1. Following the completion of this stage 1% lbs. per ton of sulphuric acid was added and the pulp conditioned for 15 minutes. The pH of the pulp at the end of this stage was 6.55. Following this stage the pulp was transferred to a 1,000 c.c. Fagergren cell and 34 lbs; per ton of sodium silicate was added. This addition of sodium silicate raised the pH to 8.0 and at the end of the 30 minute conditioning cycle the pH was 7.6. Following this stage the pulp was transferred to a 1,000 c.c. cell conditioned for 10 minutes and floated. Following the rougher float three cleaners were carried out and the following results obtained.

% by Weight Nickel Iron 1 Rougher tailings 59. l 1 .27 21.8 No. 1 Cleaner Tailings 12.2 1.39 21.5 No. 2 Cleaner Tailings 9.5 1.4 23.7 No. 3 Cleaner Tailings 5.1 1.43 25.3 Cleaner Concentrate 14.1 2.06 30.1

It will be noted that following the rougher float the cleaning stages act as a normal flotation circuit with a continuous increase in grade of a concentrate at each stage reaching a grade of 2.06 percent nickel after three stages of cleaning. Again it will be noted that at this low pH range the nickel floats differentially to the other associated minerals.

EXAMPLE IV In this Example the ore was lateritic nickel ore supplied by the Hanna Mining Company. A 1,000 gram sample was ground in a laboratory rod mill for 20 minutes at 50 percent solids with the addition of 59 lbs. per ton of sodium silicate. Following the grinding stage the pulp was transferred to a 600 c.c. Fagergren cell and conditioned for minutes with approximately 5% lbs. of fatty acid only. The pH at this stage was 9.0. Following this stage approximately l% lbs. per ton of sulphuric acid was added and the pulp conditioned for 30 minutes. The final pH was 8.3. The following metallurgical results were obtained.

by Weight Nickel Rougher Tailings 14.4 3.76 No. l Cleaner Tailings 14.3 3.41 No. 2 Cleaner Tailings 15.0 3.3 No. 3 Cleaner Tailings 15.7 3.35 Cleaner Concentrate 40.6 2.56

It will be noted that with the initial conditioning at a high pH with the collector and floating at a pH of 8.3 the nickel minerals tend to be depressed and the host rock minerals are differentially floating over the depressed nickel minerals.

EXAMPLE V This example was carried out on a lateritic nickel ore supplied by the Hanna Mining Company and again illustrates the effect of the higher pH on the depression of the nickel minerals and the tendency to float the other host rock minerals. A 1,000 gram sample was ground in a laboratory rod mill and transferred to a 600 gram laboratory Fagergren cell. Approximately 24 lbs. per ton of sodium hydroxide was added to the pulp during 110 minute conditioning cycle. In the first 100 minute conditioning approximately 5% lbs. per ton of fatty acid was added with the pH at 110. Following the 100 minute conditioning the pulp was transferred to a 600 c.c. cell and conditioned for a further minutes. The final pH was 1 1.0 and the pulp was then floated.

% by Weight Nickel lron Rougher Tailings 34.8 2.73 9.7

No. 1 Cleaner Tailings 16.5 2.67 10.7

No. 2 Cleaner Tailings 23.1 2.92 11.0

Cleaner Concentrate 25.6 1.74 10.9

EXAMPLE VI The following test on this lateritic ore supplied by the Hanna Mining Company used the higher pH range together with a gum as a dispersant, which was essentially a corn starch gum and sodium hydroxide alone as an additional dispersant and for pH control. Again at this higher pH range it will be noted that both the nickel and the iron tend to be depressed while the host rock is differentially floated. A 1,000 gram charge was ground in a laboratory rod mill at 50 percent solids for a period of 30 minutes. Following the grinding stage the pulp was transferred to a 1,000 gram cell and conditioned for 2 minutes with 3 lbs. per ton of a corn starch gum. Following this stage 6.6 lbs. per ton of sodium hydroxide was added fora conditioning period of 2 minutes raising the pH to 10.5. Following this conditioning cycle 4.5 lbs per ton of a fatty acid was added, the pulp conditioned for minutes with the further stage addition of approximately 15 lbs. per ton of sodium hydroxide raising the final pH to 1 1.6 and the pulp was then floated.

by Weight Nickel lron Rougher Tailings 35 3.40 8.7 No. 1 Cleaner Tailings 22.1 3.30 9 No. 2 Cleaner Tailings 21.9 3.17 8.7 No. 3 Cleaner Tailings 15.6 3.2 8 Cleaner Concentrate 5.5 2.01 6.1

EXAMPLE vn In this Example a 1,000 gram sample of lateritic ore V by Weight Nickel lron Rougher Tailings 21.9 3.54 10 No. l Cleaner Tailings 22.2 3.34 9.8 No. 2 Cleaner Tailings 18.2 3.21 9.0 No. 3 Cleaner Tailings 18.3 3.49 7.1 Cleaner Concentrate 19.5 2.24 5 .8

It will be noted that with the use of a high concentration of sodium silicate alone followed by the addition of a corn starch gum both the nickel and iron minerals tend to be depressed while the host rock minerals tend to float and concentrate differentially over both the nickel and the iron.

EXAMPLE Vlll In this Example the lateritic nickel ore was supplied by the Hanna Mining Company and the higher pH range was used'illustrating the differential flotation of the host rock minerals over the nickel. The ore was ground for 30 minutes using a ball charge at a density of 50 percent solids in the presence of 59 lbs. per ton of sodium silicate. Following the grinding stage the pulp was transferred to a 600 c.c. laboratory Fagergren cell and conditioned for minutes with the addition of approximately 5% lbs. per ton of fatty acid. The pH was 9.0. Following this stage 1% lbs. of sulphuric acid per ton was added and the pulp further conditioned for 30 minutes and floated at a pH of 8.5.

by Weight Nickel lron Rougher Tailings 26.8 3.64 7.8 No. l Cleaner Tailings 16.9 3.57 10.4 No. 2 Cleaner Tailings 14.9 3.37 9.8 Cleaner Concentrate 23.3 2.23 7.0

It will be noted that the differential depression of the nickel follows a very closely controlled pattern while the iron would seem to have an erratic behavior in its flotation with this reagent balance. It will be further noted that the differential flotation of the host rock over the nickel minerals is quite marked.

EXAMPLE 1X 1n the following Example the lateritic nickel ore was supplied by the International Nickel Company of Canada. A 600 gram sample was ground in a laboratory ball mill at 40 percent solids with the addition of approximately 1% lbs. per ton of nickel ammonium sulphate and 12 lbs. per ton of sodium silicate. Following the grinding stage the pulp was transferred to a 600 c.c. laboratory Fagergren cell and conditioned for a period of 10 minutes. Following this stage approximately 7 lbs. per ton of fatty acid was added to the pulp together with approximately 5 lbs. per ton of fuel oil and the pulp was conditioned for a period of 15 minutes. Following this stage approximately 1% lbs. of hydrofluoric acid per ton was added to the pulp together with approximately 1.2 lbs. of sodium fluosilicate and the pulp was conditioned for a period of 45 minutes. At the end of this stage approximately 30 lbs. per ton of sodium silicate was added to the pulp and a further conditioning cycle of 20 minutes carried out before the pulp was floated. Three stages of cleaning was carried out. The rougher tailings and cleaner concentrate only were analyzed for nickel and iron.

by Weight Nickel lron Rougher Tailings 34 l .28 16.8 Cleaner Concentrate 22.4 2.32 35.4

EXAMPLE X The following Example was carried out on the same ore as in Example IX with the only major change being substituting sulphuric acid alone for hydrofluoric acid and sodium fluosilicate. There is a direct comparison in this test on the rougher tailings only.

% lron l4.9

% Nickel by Weight Rougher Tailings In comparing the analysis of these tailings to the prior Example it will be noted that both the nickel and the iron show an increase in recovery in the rougher float indicating that sulphuric acid in the acid cycle results in better activation of the nickel than the combination of the hydrofluoric acid and sodium fluosilicate even though both circuits illustrate the clear differential in the flotation of the nickel minerals over the remaining host rock minerals.

What I claim as my invention is:

1. A process for the beneflciation of nickel bearing laterite ores comprising wet comminuting the ore to be beneflciated to a suitable degree of fineness in the presence of sufficient reagent selected from the group consisting of wetting agents and dispersing agents to provide a readily flowable pulp; subsequently conditioning the pulp with agitation in the presence of a fatty acid collecting agent at a pH which is in a range of about 8 to about 1 1.6 if it is desired to obtain a nickel enriched flotation tailing or a pH which is in a range of about 6.0 to about 8.0 if it is desired to obtain a nickel enriched flotation concentrate; and subjecting the pulp to froth flotation at substantially the pH at which said pulp has been conditioned and collecting those products of flotation which are enriched in nickel as a beneflciated nickel product.

2. The process of claim 1 wherein following comminution the pulp is subsequently treated with sulphuric acid to lower the pH thereof below 7.0 to initiate flocculation of the nickel minerals in the presence of the fatty acid collecting agent and the pulp is then conditioned with a itation in the resence of a dis ersin agent while the pl-l rises to slig litly alkaline to dispers the host rock minerals following which the pulp is subjected to froth flotation to produce a nickel enriched froth flotation concentrate.

3. .A process according to claim 1, wherein the dispersing agent is sodium silicate.

4. A process according to claim 1, wherein the dispersing agent used is sodium hydroxide.

5. A process according to claim 1, wherein the collecting agent is selected from the group consisting of fatty acid collecting agents and mixtures of fatty acid collecting agents and fuel oil.

6. The process of claim 1 wherein the pH at which said pulp is conditioned with a fatty acid is above 8.0.

7. A process according to claim 6 wherein a starch gum is present during the conditioning with a fatty acid collecting agent.

8. A process according to claim 6, wherein the dispersing agent used is sodiumhydroxide.

9. The process of claim 1 wherein, subsequent to comminution, the pulp is conditioned with agitation in the presence of sufficient reagent selected from the group consisting of wetting agents and dispersing agents to the extent necessary to enable the particles of one to behave as individual particles.

10. A process according to claim 9 wherein the dispersing agent is sodium silicate. 

2. The process of claim 1 wherein following comminution the pulp is subsequently treated with sulphuric acid to lower the pH thereof below 7.0 to initiate flocculation of the nickel minerals in the presence of the fatty acid collecting agent and the pulp is then conditioned with agitation in the presence of a dispersing agent while the pH rises to slightly alkaline to disperse the host rock minerals following which the pulp is subjected to froth flotation to produce a nickel enriched froth flotation concentrate.
 3. A process according to claim 1, wherein the dispersing agent is sodium silicate.
 4. A process according to claim 1, wherein the dispersing agent used is sodium hydroxide.
 5. A process according to claim 1, wherein the collecting agent is selected from the group consisting of fatty acid collecting agents and mixtures of fatty acid collecting agents and fuel oil.
 6. The process of claim 1 wherein the pH at which said pulp is conditioned with a fatty acid is above 8.0.
 7. A process according to claim 6 wherein a starch gum is present during the conditioning with a fatty acid collecting agent.
 8. A process according to claim 6, wherein the dispersing agent used is sodium hydroxide.
 9. The process of claim 1 wherein, subsequent to comminution, the pulp is conditioned with agitation in the presence of sufficient reagent selected from the group consisting of wetting agents and dispersing agents to the extent necessary to enable the particles of one to behave as individual particles.
 10. A process according to claim 9 wherein the dispersing agent is sodium silicate. 